I. Field of the Invention
The present invention relates to a method of sorting postal items with a view to preparing delivery rounds or “postman's walks”, such postal items being particularly but not exclusively postal items of small format, of the letter type, on a postal sorting machine having one inlet and a certain number of sorting outlets, e.g. the postal sorting machine known by the name of “Star-Duplex” from the supplier “Solystic”.
II. Discussion of the Background Art
Postman's walks with small-format postal items are currently mainly prepared on two types of equipment. A first type of equipment is constituted by very compact postal sorting machines typically having 20 sorting outlets and capable of preparing postman's walks in 3 sorting passes. Those machines are generally installed in delivery or “inward sorting” post offices.
The second type of equipment is constituted by postal machines that are installed in postal sorting centers and that have several hundred sorting outlets so as to be capable of preparing postman's walks in only 2 sorting passes.
The above-indicated postal sorting machine belongs to the second type of sorting machine. With that postal sorting machine, 40 postman's walks can be prepared simultaneously in two sorting passes, given that that machine can process about 40,000 postal items per hour from one inlet and can manage about 300 sorting outlets, and that a postman's walk can comprise up to 1000 postal items to be spread over up to 600 delivery points.
A machine of the second type makes it possible to prepare simultaneously a much larger number of postman's walks than is possible with a machine of the first type.
It is recalled that the number of delivery points in a postman's walk that can be sequenced in 2 sorting passes with a sorting machine equipped with S sorting outlets is equal to S2. In addition, after a first sorting pass, the postal items are taken from the sorting outlets and put into bins, the bins are brought in a certain order back towards the inlet of the machine, and, finally, the postal items are re-inserted into the inlet of the machine for a second pass through the machine (second sorting pass) resulting in the postal items being sequenced in the various different postman's walks.
Generally, the bins are transferred manually from the sorting outlets to the inlet of the machine. Handling the bins for returning the postal items to the inlet of the machine can take a relatively long time, during which time the sorting machine is stopped. The time required for handling a bin for returning the postal items can be estimated to be about 12 seconds, which, in view of the total number of sorting outlets, can represent several hours of bin handling time over one cycle for preparing a plurality of postman's walks on the machine. Such bin handling also requires several machine operators to be present. Such machine down times and bin handling times during which the bins are being handled by operators give rise to additional costs for preparing a postman's walk, and they delay delivery of the mail.